 |
|
|
MESC TOOL NEWS:
MESCT-CC32R-001016D
Please take note of the following problem in using cross-tool kit CC32R for the M32R family of MCUs:
- On referencing a global variable three or more times successively
-
Versions Concerned
CC32R V.1.00 Release 1 -- V.2.10 Release 1
-
Problem
When a global variable is read three or more times successively in a C-language program, a code that reads out the variable may be generated in incorrect timing (before calling a function, for example) if the program is compiled with size-oriented optimize option -Ospace selected.
- 2.1 Conditions
- This problem occurs if the following three conditions are satisfied:
- (1) -Ospace is used as an option for compilation.
- (2) A global variable is read out three or more times successively.
- (3) The value of the global variable in (2) is altered in either of the following ways before it is read out:
- (a) Calling a function that alters the global variable
- (b) Using a pointer that points to the global variable
- 2.2 Examples
- Example 1:
-------------------------------------------------------------------
int glb_data = 2; Example 1:
void
func(void)
{
glb_data = 4;
}
int
foo(void)
{
int retcode = 0;
/* Condition (3)-(a): Calling a function that alters glb_data */
func();
/* Condition (2): Referencing the global variable successively */
if(glb_data > 0 && glb_data <= 8 && glb_data != 4) {
retcode = 1 ;
}
return(retcode);
}
-------------------------------------------------------------------
- In Example 1, an if statement will be tested by referencing the value of glb_data before calling the "func()" function
- Example 2:
-------------------------------------------------------------------
int glb_data = 2; /* A global variable */
int *ptr = &glb_data; /* A pointer pointing to glb_data */
int
foo(void)
{
int retcode = 0;
/* Condition (3)-(b): Altering the value of glb_data by the pointer */
*ptr = 8;
/* Condition (2): Referencing the global variable successively */
if(glb_data > 0 && glb_data <= 8 && glb_data != 4) {
retcode = 1 ;
}
return(retcode);
}
-------------------------------------------------------------------
- In Example 2, an if statement will be tested by referencing the value of glb_data before assigning the specified value to *ptr.
-
Workaround
- This problem will be circumvented either of the following ways:
- (1) Don't use -Ospace as an option for compilation.
- (2) Reference the global variable using a temporary pointer.
- Circumvention of Example 1:
-------------------------------------------------------------------
static int glb_data = 2; /* A global variable */
void
func(void)
{
glb_data = 4;
}
int
foo(void)
{
int retcode = 0;
int *tmp_ptr = &glb_data; /* A temporary pointer pointing
to glb_data */
/* Condition (3)-(a): Calling a function that alters glb_data */
func();
/* Referencing glb_data successively using the temporary pointer */
if(*tmp_ptr > 0 && *tmp_ptr <= 8 && *tmp_ptr != 4) {
retcode = 1 ;
}
return(retcode);
}
-------------------------------------------------------------------
-
Schedule of Fixing Problem
We plan to fix this problem in our next release.
|
|
